This is a tool for evaluating bicycle transmissions with respect to gearing choices, road grade, and physical performance. Different dimensions of the problem are displayed on separate tables, with color coding by speed, cadence, and power.

By default, three tables are shown.

The Gearing table shows all gear combinations. Redundant combinations are grayed out, and the rest are sequentially numbered. Like automotive transmissions, harder gears are assigned higher numbers. Additionally, gear ratios are shown in automotive format as well, with a decimal antecedent (number of front teeth divided by rear teeth) and a common consequent of 1. Gear inches are shown, as well, to account for wheel size.

The Speed × Cadence table shows the speeds resulting from applying cadence to the available transmission gears. Additionally, table cells show the required power to maintain those speeds, taking into account system weight, aerodynamics, and road grade. Cells are colored according to speed. When power levels are within Z2-Z6 or above 1 HP, the power colors take precedence.

The Speed × Grade table mimics how a rider might behave across combinations of road grade and transmission gear. The simulation picks the fastest feasible cadence that results in power within the rider's profile. Gearing that's too easy for the given grade will cap cadence at the rider's maximum. Likewise, gearing that's too hard will cap cadence at the rider's minimum. Cells are colored by speed, with overlays highlighting the rider's power zones and preferred cadence. By following the overlays, it's possible to evaluate whether the transmission adequately matches the rider's capabilities to the terrain or climbs on the route of their choosing.

Links: Home — Steve Gribble: Cycling Power and Speed — Sheldon Brown: Gear Calculator